Thomas Fredrik Hansen

• Pienaar, Jason; Bartoszek, Krzysztof; Brahmantio, Bayu; Fierst, Janna L; Fuentes-González, Jesualdo A & Hansen, Thomas Fredrik [Show all 9 contributors for this article] (2025). Phylogenetic comparative methods for studying adaptation: the adaptation-inertia framework. Journal of Evolutionary Biology. ISSN 1010-061X. 39 (2026)(1), p. 17–17. doi: 10.1093/jeb/voaf113. Full text in Research Archive Show summary

  Abstract Phylogenetic comparative methods are a major tool for evaluating macroevolutionary hypotheses. Methods based on the mean-reverting stochastic Ornstein–Uhlenbeck process allow for modelling adaptation on a phenotypic adaptive landscape that itself evolves and where fitness peaks depend on measured characteristics of the external environment and/or other organismal traits. Here, we give an overview of the conceptual framework for the many implementations of these methods and discuss how we might interpret estimated parameters. We emphasize that the ability to model a changing adaptive landscape sets these methods apart from other approaches and discuss why this aspect captures long-term trait evolution more realistically. Recent multivariate extensions of these methods provide a powerful framework for testing evolutionary hypotheses but are also more complicated to use and interpret. We provide some guidance on their usage and put recent literature on the topic in biological rather than mathematical terms. We further show how these methods provide a starting point for modelling reciprocal selection (i.e., coevolution) between interacting lineages. We then briefly review some critiques of the methodologies. Finally, we provide some ideas for future developments that we think will be useful to evolutionary biologists.

• Isaksen, Anders; Nachtigall, Pedro Gabriel; Araya, Robin Aasegg; Beh, Jia Hao; Robinson, Samuel D. & Hansen, Thomas Fredrik [Show all 7 contributors for this article] (2025). Genome of the green-head ant, Rhytidoponera metallica, reveals mechanisms of toxin evolution in a genetically hyper-diverse eusocial species. Genome Biology. ISSN 1474-7596. 26(1). doi: 10.1186/s13059-025-03777-2. Full text in Research Archive Show summary

  Background While ants are textbook examples of eusocial animals in which altruistic behavior is maintained through kin selection, several ants form genetically diverse colonies that challenge this concept. One example is the Australian green-head ant (Rhytidoponera metallica) whose colonies harbor such extreme genetic variation that they have been speculated to represent an unstable form of eusociality. Yet, R. metallica is among the most successful ants on the Australian subcontinent. This success has been hypothesized to be partly due to the diverse venoms harbored within each colony. However, the genomic basis and evolutionary scenarios that maintain this toxin diversity remain unknown. Results To examine toxin genomic architecture, quantify individual-level genetic variation, and identify both proximate and ultimate mechanisms that have facilitated the toxin diversity in R. metallica, we generate a high-quality draft genome from a single worker. Most ectatotoxin genes are in clusters that contain evidence of multiple, complex gene-family expansions, some of which are likely explained by the presence of transposable elements. We also show that toxin regions of the genome exhibit elevated genetic variation despite being under strong selection and that this variation can translate to phenotypic diversity through toxin alleles with different functional properties. Conclusions Taken together, our results point to classical gene duplication and diversification as the main evolutionary mechanism by which the main toxin family in ant venoms evolves, suggest toxin-gene functional diversification under frequency-dependent selection maintains colony-level venom hypervariability in R. metallica, and provide new insight into the role of multi-level selection in eusocial animals.

• Pélabon, Christophe; Agudelo-Cantero, Gustavo Adolfo; Ajoy, Yimen Gerardo Araya; Bolstad, Geir Hysing; Cheng, Changde & Galis, Frietson [Show all 26 contributors for this article] (2025). Evolvability: progress and key questions. BioScience. ISSN 0006-3568. 75(12), p. 1057–1057. doi: 10.1093/biosci/biaf111. Full text in Research Archive Show summary

  Since the 1990s, evolutionary biologists have recognized the importance of explaining the ability of biological systems to evolve and how this ability itself evolves. This recognition of the need to explain evolvability emerged from an awareness that the kind and the amount of heritable variation available for natural selection require explanation. The concept of evolvability is now the focus of many research programs in diverse subdisciplines within evolutionary biology. In the present article, we first review and synthesise progress made in evolvability research. We then present key questions to set an agenda for future research on evolvability, identify challenges to answer these questions, and discuss opportunities to apply results from the evolvability research to conservation biology.

• Holstad, Agnes; Voje, Kjetil L.; Opedal, Øystein Hjorthol; Bolstad, Geir Hysing; Bourg, Salome Cassandra Sarah & Hansen, Thomas Fredrik [Show all 7 contributors for this article] (2024). Evolvability predicts macroevolution under fluctuating selection. Science. ISSN 0036-8075. 384(6696), p. 688–693. doi: 10.1126/science.adi8722. Full text in Research Archive Show summary

  Heritable variation is a prerequisite for evolutionary change, but the relevance of genetic constraints on macroevolutionary timescales is debated. By using two datasets on fossil and contemporary taxa, we show that evolutionary divergence among populations, and to a lesser extent among species, increases with microevolutionary evolvability. We evaluate and reject several hypotheses to explain this relationship and propose that an effect of evolvability on population and species divergence can be explained by the influence of genetic constraints on the ability of populations to track rapid, stationary environmental fluctuations.

• Hansen, Thomas Fredrik; Holstad, Agnes; Houle, David & Pelabon, Christophe (2024). On the importance of scale in evolutionary quantitative genetics. Evolution. ISSN 0014-3820. 78(9), p. 1523–1526. doi: 10.1093/evolut/qpae089. Full text in Research Archive Show summary

  The informed use of scales and units in evolutionary quantitative genetics is often neglected, and naïve standardizations can cause misinterpretations of empirical results. A potentially influential example of such neglect can be found in the recent book by Arnold (2023. Evolutionary quantitative genetics. Oxford University Press). There, Arnold championed the use of heritability over mean-scaled genetic variance as a measure of evolutionary potential arguing that mean-scaled genetic variances are correlated with trait means while heritabilities are not. Here, we show that Arnold’s empirical result is an artifact of ignoring the units in which traits are measured. More importantly, Arnold’s argument mistakenly assumes that the goal of mean scaling is to remove the relationship between mean and variance. In our view, the purpose of mean scaling is to put traits with different units on a common scale that makes evolutionary changes, or their potential, readily interpretable and comparable in terms of proportions of the mean.

• Hansen, Thomas Fredrik (2024). Three modes of evolution? Remarks on rates of evolution and time scaling. Journal of Evolutionary Biology. ISSN 1010-061X. 37(12), p. 1523–1537. doi: 10.1093/jeb/voae071. Full text in Research Archive Show summary

  Rates of evolution get smaller when they are measured over longer time intervals. As first shown by Gingerich, rates of morphological change measured from fossil time series show a robust minus-one scaling with time span, implying that evolutionary changes are just as large when measured over a hundred years as when measured over a hundred-thousand years. On even longer time scales, however, the scaling shifts toward a minus-half exponent consistent with evolution behaving as Brownian motion, as commonly observed in phylogenetic comparative studies. Here, I discuss how such scaling patterns arise, and I derive the patterns expected from standard stochastic models of evolution. I argue that observed shifts cannot be easily explained by simple univariate models, but require shifts in mode of evolution as time scale is changing. To illustrate this idea, I present a hypothesis about three distinct, but connected, modes of evolution. I analyze the scaling patterns predicted from this, and use the results to discuss how rates of evolution should be measured and interpreted. I argue that distinct modes of evolution at different time scales act to decouple micro- and macroevolution, and criticize various attempts at extrapolating from one to the other.

• Tsuboi, Masahito; Kopperud, Bjørn Tore; Matschiner, Michael; Grabowski, Mark Walter; Syrowatka, Christine & Pelabon, Christophe [Show all 7 contributors for this article] (2024). Antler Allometry, the Irish Elk and Gould Revisited. Evolutionary Biology. ISSN 0071-3260. 51, p. 149–165. doi: 10.1007/s11692-023-09624-1. Full text in Research Archive Show summary

  The huge antlers of the extinct Irish elk have invited evolutionary speculation since Darwin. In the 1970s, Stephen Jay Gould presented the first extensive data on antler size in the Irish elk and combined these with comparative data from other deer to test the hypothesis that the gigantic antlers were the outcome of a positive allometry that constrained large-bodied deer to have proportionally even larger antlers. He concluded that the Irish elk had antlers as predicted for its size and interpreted this within his emerging framework of developmental constraints as an explanatory factor in evolution. Here we reanalyze antler allometry based on new morphometric data for 57 taxa of the family Cervidae. We also present a new phylogeny for the Cervidae, which we use for comparative analyses. In contrast to Gould, we find that the antlers of Irish elk were larger than predicted from the allometry within the true deer, Cervini, as analyzed by Gould, but follow the allometry across Cervidae as a whole. After dissecting the discrepancy, we reject the allometric-constraint hypothesis because, contrary to Gould, we find no similarity between static and evolutionary allometries, and because we document extensive non-allometric evolution of antler size across the Cervidae.

• Bourg, Salome Cassandra Sarah; Bolstad, Geir Hysing; Griffin, Donald V.; Pelabon, Christophe & Hansen, Thomas Fredrik (2024). Directional epistasis is common in morphological divergence. Evolution. ISSN 0014-3820. 78(5), p. 934–950. doi: 10.1093/evolut/qpae029. Full text in Research Archive Show summary

  Epistasis is often portrayed as unimportant in evolution. While random patterns of epistasis may have limited effects on the response to selection, systematic directional epistasis can have substantial effects on evolutionary dynamics. Directional epistasis occurs when allele substitutions that change a trait also modify the effects of allele substitution at other loci in a systematic direction. In this case, trait evolution may induce correlated changes in allelic effects and additive genetic variance (evolvability) that modify further evolution. Although theory thus suggests a potentially important role for directional epistasis in evolution, we still lack empirical evidence about its prevalence and magnitude. Using a new framework to estimate systematic patterns of epistasis from line-crosses experiments, we quantify its effects on 197 size-related traits from diverging natural populations in 24 animal and 17 plant species. We show that directional epistasis is common and tends to become stronger with increasing morphological divergence. In animals, most traits displayed negative directionality toward larger size, suggesting that epistatic constraints reducing evolvability toward larger size. Dominance was also common but did not systematically alter the effects of epistasis.

• Grabowski, Mark Walter; Kopperud, Bjørn Tore; Tsuboi, Masahito & Hansen, Thomas Fredrik (2023). Both Diet and Sociality Affect Primate Brain-Size Evolution. Systematic Biology. ISSN 1063-5157. 72(2), p. 404–418. doi: 10.1093/sysbio/syac075. Full text in Research Archive Show summary

  Abstract Increased brain size in humans and other primates is hypothesized to confer cognitive benefits but brings costs associated with growing and maintaining energetically expensive neural tissue. Previous studies have argued that changes in either diet or levels of sociality led to shifts in brain size, but results were equivocal. Here we test these hypotheses using phylogenetic comparative methods designed to jointly account for and estimate the effects of adaptation and phylogeny. Using the largest current sample of primate brain and body sizes with observation error, complemented by newly compiled diet and sociality data, we show that both diet and sociality have influenced the evolution of brain size. Shifting from simple to more complex levels of sociality resulted in relatively larger brains, while shifting to a more folivorous diet led to relatively smaller brains. While our results support the role of sociality, they modify a range of ecological hypotheses centered on the importance of frugivory, and instead indicate that digestive costs associated with increased folivory may have resulted in relatively smaller brains. [adaptation; allometry; bayou; evolutionary trend; energetic constraints; phylogenetic comparative methods; primate brain size; Slouch; social-brain hypothesis.]

• Grabowski, Mark Walter; Pienaar, Jason; Voje, Kjetil L.; Andersson, Staffan; Fuentes-González, Jesualdo & Kopperud, Bjørn Tore [Show all 10 contributors for this article] (2023). A Cautionary Note on "A Cautionary Note on the Use of Ornstein Uhlenbeck Models in Macroevolutionary Studies". Systematic Biology. ISSN 1063-5157. 72(4), p. 955–963. doi: 10.1093/sysbio/syad012. Full text in Research Archive Show summary

  Models based on the Ornstein–Uhlenbeck process have become standard for the comparative study of adaptation. Cooper et al. (2016) have cast doubt on this practice by claiming statistical problems with fitting Ornstein–Uhlenbeck models to comparative data. Specifically, they claim that statistical tests of Brownian motion may have too high Type I error rates and that such error rates are exacerbated by measurement error. In this note, we argue that these results have little relevance to the estimation of adaptation with Ornstein–Uhlenbeck models for three reasons. First, we point out that Cooper et al. (2016) did not consider the detection of distinct optima (e.g. for different environments), and therefore did not evaluate the standard test for adaptation. Second, we show that consideration of parameter estimates, and not just statistical significance, will usually lead to correct inferences about evolutionary dynamics. Third, we show that bias due to measurement error can be corrected for by standard methods. We conclude that Cooper et al. (2016) have not identified any statistical problems specific to Ornstein–Uhlenbeck models, and that their cautions against their use in comparative analyses are unfounded and misleading. [adaptation, Ornstein–Uhlenbeck model, phylogenetic comparative method.]

• Hansen, Thomas Fredrik (2023). Variation, Inheritance, and Evolution: A Primer on Evolutionary Quantitative Genetics. In Hansen, Thomas Fredrik; Houle, David; Pavlicev, Mihaela & Pelabon, Christophe (Ed.), Evolvability A Unifying Concept in Evolutionary Biology?. MIT Press. ISSN 9780262545624. p. 73–100. doi: 10.7551/mitpress/14126.003.0007. Full text in Research Archive Show summary

  Evolutionary quantitative genetics (EQG) emerged as a research paradigm in the 1980s based on operational tools for studying variation, inheritance, and selection in field and lab studies. In this chapter, I review the conceptual foundations of EQG as well as newer developments, with particular emphasis on the representation of evolvability and constraints.

• Hansen, Thomas Fredrik & Wagner, Günter P. (2023). The Evolution of Evolvability. In Hansen, Thomas Fredrik; Houle, David; Pavlicev, Mihaela & Pelabon, Christophe (Ed.), Evolvability A Unifying Concept in Evolutionary Biology?. MIT Press. ISSN 9780262545624. p. 121–145. doi: 10.7551/mitpress/14126.003.0009. Full text in Research Archive Show summary

  The evolution of evolvability became a topic in the 1990s, and since then, it has progressed from controversies about its radical or conventional nature to a mature research program with hypotheses motivated in evolutionary theory and theoretical population genetics. Evolvability is an outcome of a variety of organismal traits, and it evolves along with these traits. In this chapter, we first review the theoretical basis for the main modes of evolution of evolvability, including adaptation at various levels; contingent evolution based on indirect, canalizing, and congruent selection; and neutral evolution, including systems drift. We then present an overview of organismal properties that may influence evolvability and provide some selected reviews of their possible modes of evolution.

• Opedal, Øystein Hjorthol; Armbruster, Scott; Hansen, Thomas Fredrik; Holstad, Agnes; Pelabon, Christophe & Andersson, Stefan [Show all 14 contributors for this article] (2023). Evolvability and trait function predict phenotypic divergence of plant populations. Proceedings of the National Academy of Sciences of the United States of America (PNAS). ISSN 0027-8424. 120(1). doi: 10.1073/pnas.2203228120. Full text in Research Archive Show summary

  Understanding the causes and limits of population divergence in phenotypic traits is a fundamental aim of evolutionary biology, with the potential to yield predictions of adaptation to environmental change. Reciprocal transplant experiments and the evaluation of optimality models suggest that local adaptation is common but not universal, and some studies suggest that trait divergence is highly constrained by genetic variances and covariances of complex phenotypes. We analyze a large database of population divergence in plants and evaluate whether evolutionary divergence scales positively with standing genetic variation within populations (evolvability), as expected if genetic constraints are evolutionarily important. We further evaluate differences in divergence and evolvability– divergence relationships between reproductive and vegetative traits and between selfing, mixed-mating, and outcrossing species, as these factors are expected to influence both patterns of selection and evolutionary potentials. Evolutionary divergence scaled positively with evolvability. Furthermore, trait divergence was greater for vegetative traits than for floral (reproductive) traits, but largely independent of the mating system. Jointly, these factors explained ~40% of the variance in evolutionary divergence. The consistency of the evolvability–divergence relationships across diverse species suggests substantial predictability of trait divergence. The results are also consistent with genetic constraints playing a role in evolutionary divergence. adaptation | evolvability | genetic constraints | macroevolution

• Pelabon, Christophe; Albertsen, Elena; Rouzic, Arnaud Le; Firmat, Cyril; Bolstad, Geir Hysing & Armbruster, W. Scott [Show all 7 contributors for this article] (2021). Quantitative assessment of observed versus predicted responses to selection. Evolution. ISSN 0014-3820. 75(9), p. 2217–2236. doi: 10.1111/evo.14284. Full text in Research Archive Show summary

  Although artificial-selection experiments seem well suited to testing our ability to predict evolution, the correspondence between predicted and observed responses is often ambiguous due to the lack of uncertainty estimates. We present equations for assessing prediction error in direct and indirect responses to selection that integrate uncertainty in genetic parameters used for prediction and sampling effects during selection. Using these, we analyzed a selection experiment on floral traits replicated in two taxa of the Dalechampia scandens (Euphorbiaceae) species complex for which G-matrices were obtained from a diallel breeding design. After four episodes of bidirectional selection, direct and indirect responses remained within wide prediction intervals, but appeared different from the predictions. Combined analyses with structural-equation models confirmed that responses were asymmetrical and lower than predicted in both species. We show that genetic drift is likely to be a dominant source of uncertainty in typically-dimensioned selection experiments in plants and a major obstacle to predicting short-term evolutionary trajectories.

• Hansen, Thomas F. & Pélabon, Christophe (2021). Evolvability: A Quantitative-Genetics Perspective. Annual Review of Ecology, Evolution and Systematics. ISSN 1543-592X. 52, p. 153–175. doi: 10.1146/annurev-ecolsys-011121-021241. Full text in Research Archive
• Hansen, Thomas Fredrik; Bolstad, Geir Hysing & Tsuboi, Masahito (2021). Analyzing Disparity and Rates of Morphological Evolution with Model-Based Phylogenetic Comparative Methods. Systematic Biology. ISSN 1063-5157. 71(5), p. 1054–1072. doi: 10.1093/sysbio/syab079. Full text in Research Archive Show summary

  Understanding variation in rates of evolution and morphological disparity is a goal of macroevolutionary research. In aphylogeneticcomparativemethods framework,we present three explicit models for linking the rate of evolution of a trait to the state of another evolving trait. This allows testing hypotheses about causal influences on rates of phenotypic evolution with phylogenetic comparative data. We develop a statistical framework for fitting the models with generalized least-squares regression and use this to discuss issues and limitations in the study of rates of evolution more generally.We showthat the power to detect effects on rates of evolution is lowin that even strong causal effects are unlikely to explain more than a few percent of observed variance in disparity. We illustrate the models and issues by testing if rates of beak-shape evolution in birds are influenced by brain size, as may be predicted from a Baldwin effect in which presumptively more behaviorally flexible large-brained species generatemore novel selection on themselves leading to higher rates of evolution. From an analysis of morphometric data for 645 species, we find evidence that both macro- and microevolution of the beak are faster in birds with larger brains, but with the caveat that there are no consistent effects of relative brain size.[Baldwin effect; beak shape; behavioral drive; bird; brain size; disparity; phylogenetic comparative method; rate of evolution.]

• Albertsen, Elena; Opedal, Øystein Hjorthol; Bolstad, Geir Hysing; Pérez-Barrales, Rocío; Hansen, Thomas F & Pelabon, Christophe [Show all 7 contributors for this article] (2020). Using ecological context to interpret spatiotemporal variation in natural selection. Evolution. ISSN 0014-3820. p. 1–16. doi: 10.1111/evo.14136. Full text in Research Archive Show summary

  Spatiotemporal variation in natural selection is expected, but difficult to estimate. Pollinator‐mediated selection on floral traits provides a good system for understanding and linking variation in selection to differences in ecological context. We studied pollinator‐mediated selection in five populations of Dalechampia scandens (Euphorbiaceae) in Costa Rica and Mexico. Using a nonlinear path‐analytical approach, we assessed several functional components of selection, and linked variation in pollinator‐mediated selection across time and space to variation in pollinator assemblages. After correcting for estimation error, we detected moderate variation in net selection on two out of four blossom traits. Both the opportunity for selection and the mean strength of selection decreased with increasing reliability of cross‐pollination. Selection for pollinator attraction was consistently positive and stronger on advertisement than reward traits. Selection on traits affecting pollen transfer from the pollinator to the stigmas was strong only when cross‐pollination was unreliable and there was a mismatch between pollinator and blossom size. These results illustrate how consideration of trait function and ecological context can facilitate both the detection and the causal understanding of spatiotemporal variation in natural selection.

• Tsuboi, Masahito; Kopperud, Bjørn Tore; Syrowatka, Christine; Grabowski, Mark Walter; Voje, Kjetil L. & Pelabon, Christophe [Show all 7 contributors for this article] (2020). Measuring Complex Morphological Traits with 3D Photogrammetry: A Case Study with Deer Antlers. Evolutionary Biology. ISSN 0071-3260. 47, p. 175–186. doi: 10.1007/s11692-020-09496-9. Full text in Research Archive Show summary

  The increasing availability of 3D-imaging technology provides new opportunities for measuring morphology. Photogrammetry enables easy 3D-data acquisition compared to conventional methods and here we assess its accuracy for measuring the size of deer antlers, a complex morphological structure. Using a proprietary photogrammetry software, we generated 3D images of antlers for 92 individuals from 29 species of cervids that vary widely in antler size and shape and used these to measure antler volume. By repeating the process, we found that the relative error averaged 8.5% of object size. Errors in converting arbitrary voxel units into real volumetric units accounted for 70% of the measurement variance and can therefore be reduced by replicating the conversion. We applied the method to clay models of known volume and found no indication of bias. The estimation was robust against variation in imaging device, distance and operator, but approximately 40 images per specimen were necessary to achieve good precision. We used the method to show that conventional measures of main-beam length are relatively poor estimators of antler volume. Using loose antlers of known weight, we also showed that the volume may be a relatively poor predictor of antler weight due to variation in bone density across species. We conclude that photogrammetry can be an efficient and accurate tool for measuring antlers, and likely many other complex morphological traits.

• Hansen, Thomas F; Solvin, Thomas Mørtvedt & Pavlicev, Mihaela (2019). Predicting evolutionary potential: A numerical test of evolvability measures. Evolution. ISSN 0014-3820. 73(4), p. 689–703. doi: 10.1111/evo.13705. Full text in Research Archive Show summary

  Despite sophisticated mathematical models, the theory of microevolution is mostly treated as a qualitative rather than a quantitative tool. Numerical measures of selection, constraints, and evolutionary potential are often too loosely connected to theory to provide operational predictions of the response to selection. In this paper, we study the ability of a set of operational measures of evolvability and constraint to predict short‐term selection responses generated by individual‐based simulations. We focus on the effects of selective constraints under which the response in one trait is impeded by stabilizing selection on other traits. The conditional evolvability is a measure of evolutionary potential explicitly developed for this situation. We show that the conditional evolvability successfully predicts rates of evolution in an equilibrium situation, and further that these equilibria are reached with characteristic times that are inversely proportional to the fitness load generated by the constraining characters. Overall, we find that evolvabilities and conditional evolvabilities bracket responses to selection, and that they together can be used to quantify evolutionary potential on time scales where the G‐matrix remains relatively constant.

• Toljagic, Olja; Voje, Kjetil L.; Matschiner, Michael; Liow, Lee Hsiang & Hansen, Thomas F (2018). Millions of Years Behind: Slow Adaptation of Ruminants to Grasslands. Systematic Biology. ISSN 1063-5157. 67(1), p. 145–157. doi: 10.1093/sysbio/syx059. Full text in Research Archive
• Houle, David; Bolstad, Geir Hysing; Linde, Kim van der & Hansen, Thomas F (2017). Mutation predicts 40 million years of fly wing evolution. Nature. ISSN 0028-0836. 548(7668), p. 447–450. doi: 10.1038/nature23473. Full text in Research Archive Show summary

  Mutation enables evolution, but the idea that adaptation is also shaped by mutational variation is controversial1–4. Simple evolutionary hypotheses predict such a relationship if the supply of mutations constrains evolution5,6, but it is not clear that constraints exist, and, even if they do, they may be overcome by long-term natural selection. Quantification of the relationship between mutation and phenotypic divergence among species will help to resolve these issues. Here we use precise data on over 50,000 Drosophilid fly wings to demonstrate unexpectedly strong positive relationships between variation produced by mutation, standing genetic variation, and the rate of evolution over the last 40 million years. Our results are inconsistent with simple constraint hypotheses because the rate of evolution is very low relative to what both mutational and standing variation could allow. In principle, the constraint hypothesis could be rescued if the vast majority of mutations are so deleterious that they cannot contribute to evolution, but this also requires the implausible assumption that deleterious mutations have the same pattern of effects as potentially advantageous ones. Our evidence for a strong relationship between mutation and divergence in a slowly evolving structure challenges the existing models of mutation in evolution.

• Armbruster, W. Scott; Bolstad, Geir Hysing; Hansen, Thomas F; Keller, Barbara; Conti, Elena & Pelabon, Christophe (2017). The measure and mismeasure of reciprocity in heterostylous flowers. New Phytologist. ISSN 0028-646X. 215, p. 906–917. doi: 10.1111/nph.14604. Full text in Research Archive Show summary

  The goal of biological measurement is to capture underlying biological phenomena in numerical form. The reciprocity index applied to heterostylous flowers is meant to measure the degree of correspondence between fertile parts of opposite sex on complementary (inter-compatible) morphs, reflecting the correspondence of locations of pollen placement on, and stigma contact with, pollinators. Pollen of typical heterostylous flowers can achieve unimpeded fertilization only on opposite-morph flowers. Thus, the implicit goal of this measurement is to assess the likelihood of ‘legitimate’ pollinations between compatible morphs, and hence reproductive fitness. Previous reciprocity metrics fall short of this goal on both empirical and theoretical grounds. We propose a new measure of reciprocity based on theory that relates floral morphology to reproductive fitness. This method establishes a scale based on adaptive inaccuracy, a measure of the fitness cost of the deviation of phenotypes in a population from the optimal phenotype. Inaccuracy allows the estimation of independent contributions of maladaptive bias (mean departure from optimum) and imprecision (within-population variance) to the phenotypic mismatch (inaccuracy) of heterostylous morphs on a common scale. We illustrate this measure using data from three species of Primula (Primulaceae). adaptive accuracy, floral dimorphisms, heterostyly, maladaptation, measurement theory, phenotypic load, pollination, Primula.

• Mayer, Christine & Hansen, Thomas F (2017). Evolvability and Robustness: A paradox restored. Journal of Theoretical Biology. ISSN 0022-5193. 430, p. 78–85. doi: 10.1016/j.jtbi.2017.07.004. Full text in Research Archive
• Hansen, Thomas F (2017). On the definition and measurement of fitness in finite populations. Journal of Theoretical Biology. ISSN 0022-5193. 419, p. 36–43. doi: 10.1016/j.jtbi.2016.12.024. Full text in Research Archive
• Opedal, Øystein Hjorthol; Bolstad, Geir Hysing; Hansen, Thomas F; Armbruster, William Scott & Pelabon, Christophe (2017). The evolvability of herkogamy: Quantifying the evolutionary potential of a composite trait. Evolution. ISSN 0014-3820. 71(6), p. 1572–1586. doi: 10.1111/evo.13258. Full text in Research Archive
• Falahati-Anbaran, Mohsen; Stenøien, Hans K.; Bolstad, Geir Hysing; Hansen, Thomas F; Pérez‐Barrales, Rocio & Armbruster, William Scott [Show all 7 contributors for this article] (2017). Novel microsatellite markers for Dalechampia scandens (Euphorbiaceae) and closely related taxa: application to studying a species complex. Plant Species Biology. ISSN 0913-557X. 32(2), p. 179–186. doi: 10.1111/1442-1984.12142. Full text in Research Archive Show summary

  We developed novel microsatellite markers for D alechampia scandens L. (Euphorbiaceae). The target plants belong to a distinct, but undescribed, species in the D . scandens species complex, characterized by small resin-producing glands. In total, 110 alleles over 36 novel markers were identified across 39 individuals from three populations. The number of alleles varied from one to seven, with an average of 3.06 ± 0.26 alleles per locus. The developed markers, along with previously developed ones for a large-glanded D . scandens species, were tested for amplification in 11 additional species of the genus D alechampia. Four markers did not produce any detectable allele in 37 individuals from two populations of the large-glanded species. Average expected heterozygosity across all small- and large-glanded specific loci was 0.36 and 0.15, for the small and large glanded populations, respectively. Cross-species amplification showed that 89% of all markers were successfully amplified in at least one of the 11 other D alechampia species. These microsatellite markers may be useful for detecting undescribed species in the D . scandens species complex, and can be used for comparative analyses of genetic structure, mating system and phylogeography of other D alechampia species.

• Malmstrøm, Martin; Matschiner, Michael; Tørresen, Ole Kristian; Star, Bastiaan; Snipen, Lars-Gustav & Hansen, Thomas F [Show all 13 contributors for this article] (2016). Evolution of the immune system influences speciation rates in teleost fishes. Nature Genetics. ISSN 1061-4036. 48(10), p. 1204–1210. doi: 10.1038/ng.3645. Full text in Research Archive Show summary

  Teleost fishes constitute the most species-rich vertebrate clade and exhibit extensive genetic and phenotypic variation, including diverse immune defense strategies. The genomic basis of a particularly aberrant strategy is exemplified by Atlantic cod, in which a loss of major histocompatibility complex (MHC) II functionality coincides with a marked expansion of MHC I genes. Through low-coverage genome sequencing (9–39×), assembly and comparative analyses for 66 teleost species, we show here that MHC II is missing in the entire Gadiformes lineage and thus was lost once in their common ancestor. In contrast, we find that MHC I gene expansions have occurred multiple times, both inside and outside this clade. Moreover, we identify an association between high MHC I copy number and elevated speciation rates using trait-dependent diversification models. Our results extend current understanding of the plasticity of the adaptive immune system and suggest an important role for immune-related genes in animal diversification.

• Hansen, Thomas F (2016). On bias and precision in metaanalysis: the error in the error. Journal of Evolutionary Biology. ISSN 1010-061X. 29, p. 1919–1921. doi: 10.1111/jeb.12947. Full text in Research Archive
• Grabowski, Mark Walter; Voje, Kjetil L. & Hansen, Thomas F (2016). Evolutionary modeling and correcting for observation error support a 3/5 brain-body allometry for primates. Journal of Human Evolution. ISSN 0047-2484. 94, p. 106–116. doi: 10.1016/j.jhevol.2016.03.001. Full text in Research Archive
• Hansen, Thomas F (2015). Evolutionary Constraints. In Losos, Jonathan (Eds.), Oxford Bibliographies in Evolutionary Biology. Oxford University Press. ISSN 9780199941728. p. 1–28. doi: 10.1093/OBO/9780199941728-0061. Full text in Research Archive
• Hansen, Thomas F (2015). Measuring gene interactions. Methods in molecular biology. ISSN 1064-3745. 1253, p. 115–143. doi: 10.1007/978-1-4939-2155-3_7. Full text in Research Archive
• Tarka, Maja; Bolstad, Geir Hysing; Wacker, Sebastian; Räsänen, Katja; Hansen, Thomas F & Pelabon, Christophe (2015). Did natural selection make the Dutch taller? A cautionary note on the importance of quantification in understanding evolution. Evolution. ISSN 0014-3820. 69(12), p. 3204–3206. doi: 10.1111/evo.12803. Full text in Research Archive
• Rouzic, Arnaud Le; Hansen, Thomas F; Gosden, Thomas P. & Svensson, Erik I. (2015). Evolutionary time-series analysis reveals the signature of frequency-dependent selection on a female mating polymorphism. The American Naturalist. ISSN 0003-0147. 185(6), p. E182–E196. doi: 10.1086/680982. Full text in Research Archive Show summary

  A major challenge in evolutionary biology is understanding how stochastic and deterministic factors interact and influence macroevolutionary dynamics in natural populations. One classical approach is to record frequency changes of heritable and visible genetic polymorphisms over multiple generations. Here, we combined this approach with a maximum likelihood–based population-genetic model with the aim of understanding and quantifying the evolutionary processes operating on a female mating polymorphism in the blue-tailed damselfly Ischnura elegans. Previous studies on this color-polymorphic species have suggested that males form a search image for females, which leads to excessive mating harassment of common female morphs. We analyzed a large temporally and spatially replicated data set of between-generation morph frequency changes in I. elegans. Morph frequencies were more stable than expected from genetic drift alone, suggesting the presence of selection toward a stable equilibrium that prevents local loss or fixation of morphs. This can be interpreted as the signature of negative frequency-dependent selection maintaining the phenotypic stasis and genetic diversity in these populations. Our novel analytical approach allows the estimation of the strength of frequency-dependent selection from the morph frequency fluctuations around their inferred long-term equilibria. This approach can be extended and applied to other polymorphic organisms for which time-series data across multiple generations are available. © 2015 University of Chicago Press

• Bolstad, Geir Hysing; Cassara, Jason A.; Marquez, Eladio; Hansen, Thomas F; Linde, Kim van der & Houle, David [Show all 7 contributors for this article] (2015). Complex constraints on allometry revealed by artificial selection on the wing of Drosophila melanogaster. Proceedings of the National Academy of Sciences of the United States of America (PNAS). ISSN 0027-8424. 112(43), p. 13284–13289. doi: 10.1073/pnas.1505357112. Full text in Research Archive Show summary

  Precise exponential scaling with size is a fundamental aspect of phenotypic variation. These allometric power laws are often invariant across taxa and have long been hypothesized to reflect developmental constraints. Here we test this hypothesis by investigating the evolutionary potential of an allometric scaling relationship in drosophilid wing shape that is nearly invariant across 111 species separated by at least 50 million years of evolution. In only 26 generations of artificial selection in a population of Drosophila melanogaster, we were able to drive the allometric slope to the outer range of those found among the 111 sampled species. This response was rapidly lost when selection was suspended. Only a small proportion of this reversal could be explained by breakup of linkage disequilibrium, and direct selection on wing shape is also unlikely to explain the reversal, because the more divergent wing shapes produced by selection on the allometric intercept did not revert. We hypothesize that the reversal was instead caused by internal selection arising from pleiotropic links to unknown traits. Our results also suggest that the observed selection response in the allometric slope was due to a component expressed late in larval development and that variation in earlier development did not respond to selection. Together, these results are consistent with a role for pleiotropic constraints in explaining the remarkable evolutionary stability of allometric scaling. allometry | artificial selection | comparative analyses | developmental constraints | pleiotropy

• Bolstad, Geir Hysing; Hansen, Thomas F; Pelabon, Christophe; Falahati-Anbaran, Mohsen; Perez-Barrales, Rocio & Armbruster, William Scott (2014). Genetic constraints predict evolutionary divergence in Dalechampia blossoms. Philosophical Transactions of the Royal Society of London. Biological Sciences. ISSN 0962-8436. 369(1649). doi: 10.1098/rstb.2013.0255. Full text in Research Archive
• Pelabon, Christophe; Firmat, Cyril Joel Patrick; Bolstad, Geir Hysing; Voje, Kjetil L.; Houle, David & Cassara, Jason [Show all 8 contributors for this article] (2014). Evolution of morphological allometry. Annals of the New York Academy of Sciences. ISSN 0077-8923. 1320(1), p. 58–75. doi: 10.1111/nyas.12470. Full text in Research Archive Show summary

  Morphological allometry refers to patterns of covariance between body parts resulting from variation in body size. Whether measured during growth (ontogenetic allometry), among individuals at similar developmental stage (static allometry), or among populations or species (evolutionary allometry), allometric relationships are often tight and relatively invariant. Consequently, it has been suggested that allometries have low evolvability and could constrain phenotypic evolution by forcing evolving species along fixed trajectories. Alternatively, allometric relationships may result from natural selection for functional optimization. Despite nearly a century of active research, distinguishing between these alternatives remains difficult, partly due to wide differences in the meaning assigned to the term allometry. In particular, a broad use of the term, encompassing any monotonic relationship between body parts, has become common. This usage breaks the connection to the proportional growth regulation that motivated Huxley's original narrow-sense use of allometry to refer to power–law relationships between traits. Focusing on the narrow-sense definition of allometry, we review here evidence for and against the allometry-as-a-constraint hypothesis. Although the low evolvability and the evolutionary invariance of the static allometric slope observed in some studies suggest a possible constraining effect of this parameter on phenotypic evolution, the lack of knowledge about selection on allometry prevents firm conclusions.

• Hansen, Thomas F (2014). Use and Misuse of Comparative Methods in the Study of Adaptation. In Zsolt, Garamszegi László (Eds.), Modern Phylogenetic Comparative Methods and Their Application in Evolutionary Biology. Springer. ISSN 9783662435502. p. 351–379. doi: 10.1007/978-3-662-43550-2_14. Full text in Research Archive
• Voje, Kjetil L.; Hansen, Thomas F; Egset, Camilla Kalvatn; Bolstad, Geir Hysing & Pelabon, Christophe (2014). Allometric constraints and the evolution of allometry. Evolution. ISSN 0014-3820. 68(3), p. 866–885. doi: 10.1111/evo.12312. Full text in Research Archive
• Firmat, Cyril Joel Patrick; Lozano-Fernandez, I; Agusti, J; Bolstad, Geir Hysing; Cuenca-Bescos, G & Hansen, Thomas F [Show all 7 contributors for this article] (2014). Walk the line: 600 000 years of molar evolution constrained by allometry in the fossil rodent Mimomys savini. Philosophical Transactions of the Royal Society of London. Biological Sciences. ISSN 0962-8436. 369(1649). doi: 10.1098/rstb.2014.0057. Full text in Research Archive
• Armbruster, William Scott; Pelabon, Christophe; Bolstad, Geir Hysing & Hansen, Thomas F (2014). Integrated phenotypes: Understanding trait covariation in plants and animals. Philosophical Transactions of the Royal Society of London. Biological Sciences. ISSN 0962-8436. 369(1649). doi: 10.1098/rstb.2013.0245. Full text in Research Archive
• Voje, Kjetil Lysne; Mazzarella, Anna Virginia Black; Hansen, Thomas F; Østbye, Kjartan; Klepaker, Tom Olav & Bass, Arthur [Show all 10 contributors for this article] (2013). Adaptation and constraint in a stickleback radiation. Journal of Evolutionary Biology. ISSN 1010-061X. 26(11), p. 2396–2414. doi: 10.1111/jeb.12240. Full text in Research Archive
• Falahati-Anbaran, Mohsen; Stenøien, Hans K.; Pelabon, Christophe; Bolstad, Geir Hysing; Perez-Barrales, Rocio & Hansen, Thomas F [Show all 7 contributors for this article] (2013). Development of microsatellite markers for the neotropical vine Dalechampia scandens (Euphorbiaceae). American Journal of Botany. ISSN 0002-9122. 1(6). doi: 10.3732/apps.1200492. Full text in Research Archive
• Voje, Kjetil Lysne & Hansen, Thomas F (2013). Evolution of static allometries: adaptive change in allometric slopes of eye span in stalk-eyed flies. Evolution. ISSN 0014-3820. 67(2), p. 453–467. doi: 10.1111/j.1558-5646.2012.01777.x. Full text in Research Archive
• Perez-Barrales, Rocio; Bolstad, Geir Hysing; Pelabon, Christophe; Hansen, Thomas F & Armbruster, William Scott (2013). Pollinators and seed predators generate conflicting selection on Dalechampia blossoms. Oikos. ISSN 0030-1299. 122(10), p. 1411–1428. doi: 10.1111/j.1600-0706.2013.20780.x. Full text in Research Archive
• Rouzic, Arnaud Le; Alvarez-Castro, Jose M. & Hansen, Thomas F (2013). The Evolution of Canalization and Evolvability in Stable and Fluctuating Environments. Evolutionary Biology. ISSN 0071-3260. 40(3), p. 317–340. doi: 10.1007/s11692-012-9218-z. Full text in Research Archive
• Hansen, Thomas F (2013). Why epistasis is important for selection and adaptation. Evolution. ISSN 0014-3820. 67(12), p. 3501–3511. doi: 10.1111/evo.12214. Full text in Research Archive
• Egset, Camilla Kalvatn; Hansen, Thomas F; Rouzic, Arnaud Le; Bolstad, Geir Hysing; Rosenqvist, Gunilla & Pelabon, Christophe (2012). Artificial selection on allometry: change in elevation but not slope. Journal of Evolutionary Biology. ISSN 1010-061X. 25(5), p. 938–948. doi: 10.1111/j.1420-9101.2012.02487.x. Full text in Research Archive Show summary

  To what extent within-species (static) allometries constitute a constraint on evolution is the subject of a long-standing debate in evolutionary biology. A prerequisite for the constraint hypothesis is that static allometries are hard to change. Several studies have attempted to test this hypothesis with artificial-selection experiments, but their results remain inconclusive due to various methodological issues. Here, we present results from an experiment in which we selected independently on the slope and the elevation of the allometric relationship between caudal-fin size and body size in male guppies (Poecilia reticulata). After three episodes of selection, the allometric elevation (i.e. intercept at constant slope) had diverged markedly between the lines selected to increase or decrease it, and showed a realized heritability of 50%. In contrast, the allometric slope remained unaffected by selection. These results suggest that the allometric elevation is more evolvable than the allometric slope, this latter representing a potential constraint on adaptive trait evolution. To our knowledge, this study is the first artificial-selection experiment that directly tests the evolvability of static allometric slopes.

• Armbruster, W. Scott; Hansen, Thomas F; Bolstad, Geir Hysing; Perez-Barrales, Rocio & Pelabon, Christophe (2012). Adaptive accuracy and adaptive landscapes. In Svensson, Erik I. & Calsbeek, Ryan (Ed.), The adaptive landscape in evolutionary biology. Oxford University Press. ISSN 9780199595372. p. 150–168. doi: 10.1093/oso/9780199595372.003.0010. Full text in Research Archive
• Hansen, Thomas F (2012). Adaptive Landscapes and Macroevolutionary Dynamics. In Svensson, Erik I. & Calsbeek, Ryan (Ed.), The adaptive landscape in evolutionary biology. Oxford University Press. ISSN 9780199595372. p. 205–226. doi: 10.1093/oso/9780199595372.003.0013. Full text in Research Archive
• Hansen, Thomas F & Bartoszek, Krzysztof (2012). Interpreting the Evolutionary Regression: The Interplay Between Observational and Biological Errors in Phylogenetic Comparative Studies. Systematic Biology. ISSN 1063-5157. 61(3), p. 413–425. doi: 10.1093/sysbio/syr122. Full text in Research Archive
• Bartoszek, Krzystof; Pienaar, Jason; Mostad, Petter; Andersson, Staffan & Hansen, Thomas F (2012). A phylogenetic comparative method for studying multivariate adaptation. Journal of Theoretical Biology. ISSN 0022-5193. 314, p. 204–215. doi: 10.1016/j.jtbi.2012.08.005. Full text in Research Archive
• Pelabon, Christophe; Thöne, Patrick; Hansen, Thomas F & Armbruster, William Scott (2012). Signal honesty and cost of pollinator rewards in Dalechampia scandens (Euphorbiaceae). Annals of Botany. ISSN 0305-7364. 109(7), p. 1331–1339. doi: 10.1093/aob/mcs091. Full text in Research Archive
• Escudero, Marcial; Hipp, Andrew L.; Hansen, Thomas F; Voje, Kjetil Lysne & Luceño, Modesto (2012). Selection and inertia in the evolution of holocentric chromosomes in sedges (Carex, Cyperaceae). New Phytologist. ISSN 0028-646X. 195(1), p. 237–247. doi: 10.1111/j.1469-8137.2012.04137.x. Full text in Research Archive
• Houle, David; Pelabon, Christophe; Wagner, Günter P. & Hansen, Thomas F (2011). Measurement and meaning in biology. The Quarterly review of biology. ISSN 0033-5770. 86(1), p. 3–34. doi: 10.1086/658408. Full text in Research Archive
• Rouzic, Arnaud Le; Østbye, Kjartan; Klepaker, Tom Olav; Hansen, Thomas F; Bernatchez, Louis & Schluter, Dolph [Show all 7 contributors for this article] (2011). Strong and consistent natural selection associated with armour reduction in sticklebacks. Molecular Ecology. ISSN 0962-1083. 20, p. 2483–2493. doi: 10.1111/j.1365-294X.2011.05071.x. Full text in Research Archive
• Uyeda, Josef; Hansen, Thomas F; Arnold, Stevan J & Pienaar, Jason (2011). The million-year wait for macroevolutionary bursts. Proceedings of the National Academy of Sciences of the United States of America (PNAS). ISSN 0027-8424. 108(38), p. 15908–15913. doi: 10.1073/pnas.1014503108. Full text in Research Archive
• Rouzic, Arnaud Le; Houle, David & Hansen, Thomas F (2011). A modelling framework for the analysis of artificial-selection time series. Genetics Research. ISSN 0016-6723. 93(2), p. 155–173. doi: 10.1017/s0016672311000024. Full text in Research Archive
• Hansen, Thomas F (2011). Epigenetics: Adaptation or Contingency? Epigenetics: Linking genotype and phenotype in development and evolution. University of California Press. ISSN 9780520267091. p. 357–376. Full text in Research Archive
• Pelabon, Christophe; Armbruster, William Scott & Hansen, Thomas F (2011). Experimental evidence for the Berg hypothesis: vegetative traits are more sensitive than pollination traits to environmental variation. Functional Ecology. ISSN 0269-8463. 25(1), p. 247–257. doi: 10.1111/j.1365-2435.2010.01770.x. Full text in Research Archive
• Hansen, Thomas F & Voje, Kjetil Lysne (2011). DEVIATION FROM THE LINE OF LEAST RESISTANCE DOES NOT EXCLUDE GENETIC CONSTRAINTS: A COMMENT ON BERNER ET AL. (2010). Evolution. ISSN 0014-3820. 65(6), p. 1821–1822. doi: 10.1111/j.1558-5646.2011.01281.x. Full text in Research Archive
• Pavlicev, Mihaela & Hansen, Thomas F (2011). Genotype-Phenotype Maps Maximizing Evolvability: Modularity Revisited. Evolutionary Biology. ISSN 0071-3260. 38(4), p. 371–389. doi: 10.1007/s11692-011-9136-5. Full text in Research Archive
• Pavlicev, Mihaela; Rouzic, Arnaud Le; Cheverud, James; P., Wagner Günter & Hansen, Thomas F (2010). Directionality of Epistasis in a Murine Intercross Population. Genetics. ISSN 0016-6731. 185(4), p. 1489–1505. doi: 10.1534/genetics.110.118356. Full text in Research Archive
• Bolstad, Geir H; Armbruster, W. Scott; Pelabon, Christophe; Pérez-Barrales, R & Hansen, Thomas F (2010). Direct selection at the blossom level on floral reward by pollinators in a natural population of Dalechampia schottii: full-disclosure honesty? New Phytologist. ISSN 0028-646X. 188(2), p. 370–384. doi: 10.1111/j.1469-8137.2010.03429.x. Full text in Research Archive Show summary

  • Both floral rewards and advertisements can be important in the attraction of pollinators, but few studies have separated the individual contributions of rewards and advertisements to fitness. • Here, we investigated selection by pollinators on individual blossoms in Dalechampia schottii. This Neotropical vine, endemic to the Yucata´n Peninsula, rewards bees by secreting fully visible, deep-blue resin from a gland subtended by two conspicuous petaloid bracts that may play the role of advertisement. • We used contextual analysis to build a fitness function for four morphological traits of individual blossoms: the amount of the reward as measured by gland area; the size of the advertisement trait as measured by bract length; the flower-pollinator fit as measured by the shortest distance between reward and stigma; and the potential for self-pollination as measured by the shortest distance between anthers and stigma. • Larger gland area and increased potential for self-pollination directly increased the seed production of individual blossoms. However, bract size or flower-pollinator fit did not influence the number of seeds produced by blossoms. Therefore, in this Dalechampia species, pollinators seem to select directly on the reward of individual blossoms but not on the advertising bracts.

• Pelabon, Christophe; Hansen, TF; Carter, Ashley J.R. & Houle, David (2010). EVOLUTION OF VARIATION AND VARIABILITY UNDER FLUCTUATING, STABILIZING, AND DISRUPTIVE SELECTION. Evolution. ISSN 0014-3820. 64(7), p. 1912–1925. doi: 10.1111/j.1558-5646.2010.00979.x. Full text in Research Archive
• Labra, Antonieta; Voje, Kjetil Lysne; Seligmann, Hervé & Hansen, Thomas F (2010). Evolution of the third eye: a phylogenetic comparative study of parietal-eye size as an ecophysiological adaptation in Liolaemus lizards. Biological Journal of the Linnean Society. ISSN 0024-4066. 101(4), p. 870–883. doi: 10.1111/j.1095-8312.2010.01541.x. Full text in Research Archive
• Fierst, Janna & Hansen, Thomas F (2010). Genetic architecture and postzygotic reproductive isolation: Evolution of Bateson-Dobzhansky-Muller incompatibilities in a polygenic Model. Evolution. ISSN 0014-3820. 64(3), p. 675–693. doi: 10.1111/j.1558-5646.2009.00861.x. Full text in Research Archive
• Rouzic, Arnaud Le; Skaug, Hans Julius & Hansen, Thomas F. (2010). Estimating genetic architectures from artificial-selection responses: A random-effect framework. Theoretical Population Biology. ISSN 0040-5809. 77(2), p. 119–130. doi: 10.1016/j.tpb.2009.12.003. Full text in Research Archive
• Armbruster, William Scott; Pelabon, Christophe; Hansen, Thomas & Bolstad, Geir Hysing (2009). Macroevolutionary patterns of pollination accuracy: a comparison of three genera. New Phytologist. ISSN 0028-646X. 183(3), p. 600–617. doi: 10.1111/j.1469-8137.2009.02930.x. Full text in Research Archive
• Hansen, Thomas F & Houle, David (2009). Corrigendum. Journal of Evolutionary Biology. ISSN 1010-061X. 22(4), p. 913–915. doi: 10.1111/j.1420-9101.2009.01715.x. Full text in Research Archive
• Labra, Antonieta; Pienaar, Jason & Hansen, Thomas F (2009). Evolution of Thermal Physiology in Liolaemus Lizards: Adaptation, Phylogenetic Inertia, and Niche Tracking. The American Naturalist. ISSN 0003-0147. 174(2), p. 204–220. doi: 10.1086/600088. Full text in Research Archive
• Armbruster, William Scott; Hansen, TF; Pelabon, Christophe; Pérez-Barrales, R; Perez-Barrales, R & Maad, Johanne (2009). The adaptive accuracy of flowers: measurement and microevolutionary patterns. Annals of Botany. ISSN 0305-7364. 103(9), p. 1529–1545. doi: 10.1093/aob/mcp095. Full text in Research Archive
• Hansen, Thomas F; Pienaar, J & Orzack, SH (2008). A comparative method for studying adaptation to a randomly evolving environment. Evolution. ISSN 0014-3820. 62, p. 1965–1977. doi: 10.1111/j.1558-5646.2008.00412.x. Full text in Research Archive

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• Hansen, Thomas Fredrik; Houle, David; Pavlicev, Mihaela & Pelabon, Christophe (2023). Evolvability A Unifying Concept in Evolutionary Biology? MIT Press. ISBN 9780262545624. 395 p. doi: 10.7551/mitpress/14126.001.0001. Full text in Research Archive Show summary

  Essays on evolvability from the perspectives of quantitative and population genetics, evolutionary developmental biology, systems biology, macroevolution, and the philosophy of science. Evolvability—the capability of organisms to evolve—wasn't recognized as a fundamental concept in evolutionary theory until 1990. Though there is still some debate as to whether it represents a truly new concept, the essays in this volume emphasize its value in enabling new research programs and facilitating communication among the major disciplines in evolutionary biology. The contributors, many of whom were instrumental in the development of the concept of evolvability, synthesize what we have learned about it over the past thirty years. They focus on the historical and philosophical contexts that influenced the emergence of the concept and suggest ways to develop a common language and theory to drive further evolvability research. The essays, drawn from a workshop on evolvability hosted in 2019–2020 by the Center of Advanced Study at the Norwegian Academy of Science and Letters, in Oslo, provide scientific and historical background on evolvability. The contributors represent different disciplines of evolutionary biology, including quantitative and population genetics, evolutionary developmental biology, systems biology, and macroevolution, as well as the philosophy of science. This plurality of approaches allows researchers in disciplines as diverse as developmental biology, molecular biology, and systems biology to communicate with those working in mainstream evolutionary biology. The contributors also discuss key questions at the forefront of research on evolvability. Contributors:J. David Aponte, W. Scott Armbruster, Geir H. Bolstad, Salomé Bourg, Ingo Brigandt, Anne Calof, James M. Cheverud, Josselin Clo, Frietson Galis, Mark Grabowski, Rebecca Green, Benedikt Hallgrímsson, Thomas F. Hansen, Agnes Holstad, David Houle, David Jablonski, Arthur Lander, Arnaud LeRouzic, Alan C. Love, Ralph Marcucio, Michael B. Morrissey, Laura Nuño de la Rosa, Øystein H. Opedal, Mihaela Pavličev, Christophe Pélabon, Jane M. Reid, Heather Richbourg, Jacqueline L. Sztepanacz, Masahito Tsuboi, Cristina Villegas, Marta Vidal-García, Kjetil L. Voje, Andreas Wagner, Günter P. Wagner, Nathan M. Young

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• Hansen, Thomas Fredrik (2025). Evolvability. In Russo, Claudia Augusta De Moraes & Wolf, Jason B. (Ed.), Encyclopedia of Evolutionary Biology. Second Edition. Elsevier. ISSN 9780443157516. p. 179–189. doi: 10.1016/b978-0-443-15750-9.00047-1. Full text in Research Archive
• Houle, David; Pelabon, Christophe; Pavlicev, Mihaela & Hansen, Thomas Fredrik (2023). Conclusion: Is Evolvability a New and Unifying Concept? In Hansen, Thomas Fredrik; Houle, David; Pavlicev, Mihaela & Pelabon, Christophe (Ed.), Evolvability A Unifying Concept in Evolutionary Biology?. MIT Press. ISSN 9780262545624. p. 373–388. Full text in Research Archive Show summary

  Essays on evolvability from the perspectives of quantitative and population genetics, evolutionary developmental biology, systems biology, macroevolution, and the philosophy of science. Evolvability—the capability of organisms to evolve—wasn't recognized as a fundamental concept in evolutionary theory until 1990. Though there is still some debate as to whether it represents a truly new concept, the essays in this volume emphasize its value in enabling new research programs and facilitating communication among the major disciplines in evolutionary biology. The contributors, many of whom were instrumental in the development of the concept of evolvability, synthesize what we have learned about it over the past thirty years. They focus on the historical and philosophical contexts that influenced the emergence of the concept and suggest ways to develop a common language and theory to drive further evolvability research. The essays, drawn from a workshop on evolvability hosted in 2019–2020 by the Center of Advanced Study at the Norwegian Academy of Science and Letters, in Oslo, provide scientific and historical background on evolvability. The contributors represent different disciplines of evolutionary biology, including quantitative and population genetics, evolutionary developmental biology, systems biology, and macroevolution, as well as the philosophy of science. This plurality of approaches allows researchers in disciplines as diverse as developmental biology, molecular biology, and systems biology to communicate with those working in mainstream evolutionary biology. The contributors also discuss key questions at the forefront of research on evolvability. Contributors:J. David Aponte, W. Scott Armbruster, Geir H. Bolstad, Salomé Bourg, Ingo Brigandt, Anne Calof, James M. Cheverud, Josselin Clo, Frietson Galis, Mark Grabowski, Rebecca Green, Benedikt Hallgrímsson, Thomas F. Hansen, Agnes Holstad, David Houle, David Jablonski, Arthur Lander, Arnaud LeRouzic, Alan C. Love, Ralph Marcucio, Michael B. Morrissey, Laura Nuño de la Rosa, Øystein H. Opedal, Mihaela Pavličev, Christophe Pélabon, Jane M. Reid, Heather Richbourg, Jacqueline L. Sztepanacz, Masahito Tsuboi, Cristina Villegas, Marta Vidal-García, Kjetil L. Voje, Andreas Wagner, Günter P. Wagner, Nathan M. Young

• Hansen, Thomas Fredrik; Pelabon, Christophe; Houle, David & Pavlicev, Mihaela (2023). Introduction: Evolvability. In Hansen, Thomas Fredrik; Houle, David; Pavlicev, Mihaela & Pelabon, Christophe (Ed.), Evolvability A Unifying Concept in Evolutionary Biology?. MIT Press. ISSN 9780262545624. p. 1–10. Full text in Research Archive Show summary

  Essays on evolvability from the perspectives of quantitative and population genetics, evolutionary developmental biology, systems biology, macroevolution, and the philosophy of science. Evolvability—the capability of organisms to evolve—wasn't recognized as a fundamental concept in evolutionary theory until 1990. Though there is still some debate as to whether it represents a truly new concept, the essays in this volume emphasize its value in enabling new research programs and facilitating communication among the major disciplines in evolutionary biology. The contributors, many of whom were instrumental in the development of the concept of evolvability, synthesize what we have learned about it over the past thirty years. They focus on the historical and philosophical contexts that influenced the emergence of the concept and suggest ways to develop a common language and theory to drive further evolvability research. The essays, drawn from a workshop on evolvability hosted in 2019–2020 by the Center of Advanced Study at the Norwegian Academy of Science and Letters, in Oslo, provide scientific and historical background on evolvability. The contributors represent different disciplines of evolutionary biology, including quantitative and population genetics, evolutionary developmental biology, systems biology, and macroevolution, as well as the philosophy of science. This plurality of approaches allows researchers in disciplines as diverse as developmental biology, molecular biology, and systems biology to communicate with those working in mainstream evolutionary biology. The contributors also discuss key questions at the forefront of research on evolvability. Contributors:J. David Aponte, W. Scott Armbruster, Geir H. Bolstad, Salomé Bourg, Ingo Brigandt, Anne Calof, James M. Cheverud, Josselin Clo, Frietson Galis, Mark Grabowski, Rebecca Green, Benedikt Hallgrímsson, Thomas F. Hansen, Agnes Holstad, David Houle, David Jablonski, Arthur Lander, Arnaud LeRouzic, Alan C. Love, Ralph Marcucio, Michael B. Morrissey, Laura Nuño de la Rosa, Øystein H. Opedal, Mihaela Pavličev, Christophe Pélabon, Jane M. Reid, Heather Richbourg, Jacqueline L. Sztepanacz, Masahito Tsuboi, Cristina Villegas, Marta Vidal-García, Kjetil L. Voje, Andreas Wagner, Günter P. Wagner, Nathan M. Young

• Albertsen, Elena; Opedal, Øystein H.; Bolstad, Geir Hysing; Perez-Barrales, Rocio; Hansen, Thomas F & Pelabon, Christophe [Show all 7 contributors for this article] (2020). Using ecological context to interpret spatiotemperal variation in natural selection. Full text in Research Archive
• Bolstad, Geir Hysing; Albertsen, Elena; Perez-Barrales, Rocio; Opedal, Øystein Hjorthol; Armbruster, Scott & Pelabon, Christophe [Show all 7 contributors for this article] (2019). Benefits of using non-linear path analysis for estimating natural selection. Full text in Research Archive
• Hansen, Thomas F (2017). A review of "Genes and Evolution. Current topics in developmental Biology, Volume 119, Edited by Virginie Orgogozo". The Quarterly review of biology. ISSN 0033-5770. 92, p. 479–480. Full text in Research Archive
• Mayer, Christine & Hansen, Thomas F (2017). Evovability and Robustness in Models of Pattern Formation. Full text in Research Archive
• Mayer, Christine & Hansen, Thomas F (2016). Resolving the relationship between evolvability and robustness using Boolean Genotype-Phenotype Maps. Full text in Research Archive
• Hansen, Thomas F (2016). Evolvability, Quantitative Genetics of. In Kliman, Richard M. (Eds.), Encyclopedia of Evolutionary Biology. Elsevier. ISSN 9780128000496. p. 83–89. doi: 10.1016/B978-0-12-800049-6.00042-1. Full text in Research Archive
• Hansen, Thomas F (2016). Epistasis. In Rosa, Laura Nuno de la & Müller, Gerd (Ed.), Evolutionary Developmental Biology. A Reference Guide. Springer Publishing Company. ISSN 9783319330389. p. 1–14. doi: 10.1007/978-3-319-33038-9_53-1. Full text in Research Archive
• Svendsen, Ida Krogsgaard & Hansen, Thomas F (2016). Effects of climate change on biogeography. Full text in Research Archive
• Kopperud, Bjørn Tore & Hansen, Thomas F (2016). Artiodactyl brain size evolution. Full text in Research Archive
• Albertsen, Elena; Pelabon, Christophe; Rouzic, Arnaud Le; Firmat, Cyril; Hansen, Thomas F & Bolstad, Geir Hysing [Show all 7 contributors for this article] (2016). Can we predict direct and correlated response to selection beyond the first generation? Full text in Research Archive
• Kopperud, Bjørn Tore & Hansen, Thomas F (2015). The ungulate brain: A comparative analysis. Full text in Research Archive
• Tarka, Maja; Pelabon, Christophe; Hansen, Thomas F & Sæther, Bernt-Erik (2015). Intralocus sexual conflict and the evolution of sexual dimorphism. Full text in Research Archive
• Mayer, Christine & Hansen, Thomas F (2015). Genotype-Phenotype Maps: Exploring evolvability and robustness by combining a multilinear framework with Boolean networks. Full text in Research Archive
• Mayer, Christine & Hansen, Thomas F (2015). Genotype-Phenotype maps: Exploring evolvability and robustness by combining a multilinear framework with Boolean networks. Full text in Research Archive
• Mayer, Christine & Hansen, Thomas F (2015). Modeling Genotype-Phenotype Maps by combining a multilinear model with Boolean Networks. Full text in Research Archive
• Hansen, Thomas F (2015). Fitness. In Losos, Jonathan (Eds.), Oxford Bibliographies in Evolutionary Biology. Oxford University Press. ISSN 9780199941728. Full text in Research Archive
• Hansen, Thomas F (2015). Forståelse og misforståelse av arvelighet gjennom historien. In Hessen, Dag Olav; Lie, Thore & Stenseth, Nils Christian (Ed.), Mendels arv - Genetikkens æra. Gyldendal Norsk Forlag A/S. ISSN 9788205458185. p. 45–79. Full text in Research Archive
• Liow, Lee Hsiang & Hansen, Thomas F (2013). The Macroevolution Group: monkeys, horses, moss- and other animals (and plants). Full text in Research Archive
• Labra, Antonieta; Voje, Kjetil Lysne; Seligmann, Hervé & Hansen, Thomas F (2011). Erratum bij_1599 237..238 Evolution of the third eye: a phylogenetic comparative study of parietal-eye size as an ecophysiological adaptation in Liolaemus lizards. Biological Journal of the Linnean Society. ISSN 0024-4066. 102(1), p. 237–238. doi: 10.1111/j.1095-8312.2010.01599.x. Full text in Research Archive
• Hessen, Dag Olav; Stenseth, Nils Christian & Hansen, Thomas F (2010). Anmeldelser: Menneskets vei. [Internet]. Tidsskrift for Den norske legeforening. Full text in Research Archive
• Pavlicev, Mihaela; Cheverud, James & Hansen, Thomas F (2010). The relationship between pleiotropy and evolvability. Integrative and Comparative Biology. ISSN 1540-7063. 50, p. E135–E135. Full text in Research Archive
• Hansen, Thomas F (2009). Etter neodarwinismen: Hovedtrekk i evolusjonsteorien 1959-2009. In Hessen, Dag Olav; Lie, Thore & Stenseth, Nils Christian (Ed.), Darwin - Verden ble aldri den samme. Gyldendal Litteratur. ISSN 9788205390348. p. 83–132. Full text in Research Archive
• Hansen, Thomas F (2008). Macroevolutionary quantitative genetics? A comment on Polly (2008). Evolutionary Biology. ISSN 0071-3260. 35, p. 182–185. doi: 10.1007/s11692-008-9027-6. Full text in Research Archive
• Fierst, Janna & Hansen, Thomas F (2008). The Genetic Architecture of Reproductive Isolation. Full text in Research Archive

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